Method of starting alternating-current motors.



No. 851,890.- PATENTED APR. 30, 1907.

W. A. LAYMAN.

METHOD OP STARTING ALTERNATINGURRBNT MOTORS.

APPLIGATION'HLED AUG. s, 190e.

WALDO A. LAYMAN, OF ST. LOUIS, MISSOURI.

IVIETHOD OF STARTING ALTERNATINGBGUFHENT WQTORS.

Specification of Le 'sters Eatent.

Iatented Apri 30, 1307.

Application Jfiled August 6,1906. Serial No. 329.351.

e have invented a certain new and useful Method of Starting. Alternating-Current Motors, of which the following is such a full, clear,.and exact description as will enable any one skilled in theart to which it appertains to make and use the same, reference being had to the accompanying drawings, forming part of this specification.

My invention relates to alternating current motors and especially to that type of such motors operated by single phase alternating current and in which the rotary member is started from rest under load as a repulsion or series motor or some equivalent of these types or combination thereof, and operates when running under load atA normal speed as an induction motor. In one form of this type of motor well known in the art, the rotary member, or armature, is provided with means for'predetermining the position of the poles of such member with respect to those of the stationary member or field. vSuch means commonly consist of a commutator and brushes, the latter being usually connected together on a locally Vclosed or short circuit.

The object of my invention is to prevent,

as far as possible, the rush of current which occurs in theline and the motor circuits at startiligln'der load and to keep the current as nearlyuniform as possible duringthe operation of starting, at the same time obtaining a high and practically uniform starting f torque.

In the drawing accompanying this application I have illustrated one form of apparatus adapted for carrying out my method. In it Figure 1 is a diagram of such an apparatus and, F ig. 2 is a diagram of curves, which will be found convenient in explaining the method which I employ.

Referring to Fig. 1, 10 is the field core of the motor provided with. the usual winding 11. .l2 is the armature core provided with the customary winding 13, having leads 11i, connected with the segments of the commutator l5, on which bear brushes, I6, connected togctherby a conductor 17. All of these parts are already well known in the art and l do not therefore more particularly describe them here. 20 and 2,1 are the line wires carr 'ng the current to the motor and across t em is connected an autotransformer in the switch arm 28.

manner now to be described: The line wire 20 is connected by a wire 22 with one of the terminals of the motor field winding and the line wire 2l is connected at 23 to an intermediate point 4in the coil of the autotransformer 24. Taps 26 are led out at intervals from the coil :24 and are provided with contact points 27 within reach of the switch arm 2S, pivoted at 2l) to move over said taps. 3l is an auxiliary coil of the autotransformer which is provided with taps 32 leading to contact points 33, also within reach of the 35 is a conductor leading from the line wire 21 to a contact point 37, also within the reach of the switch arm 28. 38 is a conductor connecting switch arm 28 vwith the remaining terminal of the motor field winding 11, and 39 is a conductor connecting the right hand end of the coil 24 with the right hand end of the auxiliary coil 31. 40 indicates a conducting ring adapted to be clamped by any suitable means upon all of the segments of the commutator l5 to shortcircuit individual coils of the armature winding I3 when the armature reaches full nor` mal running speed under load, after the manner already well known in the art in connection with motors of this type. TWhen such motors are operated in the manner heretofore in use they have customarily taken at the first instant of starting about,V 200 to 25,0 per cent. of the current required when the motor is ruiming at full or normal running speed under load, that is, when the short-circuiting ring 40 is clamped upon the armature, and have developed about 200 to 400`per cent.A of the torque of the motor at normal speed under load. As the motor climbs from initial rotation tospeed, .the current falls off gradually from its high value at initial starting to normal full load currentwhen normal running speed under load is attained, while the torque first rises until it reaches a maximum at approximately one-third of normalvrunuing speed under load and then falls to full load torque when normal running speed under load has been obtained. This is illustrated .in the diagram of Fig. 2 where the lines` i) X and O Y are the customary abseissa and ordinate and Z represents the point at which normal running speed under load is attained and the contact ring 40 clamped upon the commutator. llere the line A indicates thc current usually taken when the motor starts, as has heretofore been customary. vvB represents the rise and IOO ' designed to operate at full speed -i the torque under such circumstances and C the usual constant voltage or normal or erating voltage of the current supplied to tfie motor, i. e., the voltage at which it is under load normal operating voltage. With this method of ting it Will be observed: First. "lfhat the initial torque is higher than necessary and the initial current very much more than desired, giving rise to a disturbance of the circuit and too much sparking at the commutator at the iirst instant of starting. Second. That on aijiproaehing full speed under load the torque drops to practically full load torque.

this particular instance it is desired to maintain not less than one and one-lialf times full load torque from starting to full normal speed, at the same time not using a larger starting current than absolutely required. lhis may be done by employing a reduced voltage at the 'first instant of starting and gradually increasing this voltage immediately after initial rotation and as normal running speed under load is being gained. lWhen this point of normal speed under load is reached, that is, when the short-circuiting ring l0 is clamped upon the commutator l5, there is no longer need of this increased voltage and it can therefore be gradually reduced to the normal operating voltage at which the motor is designed to operate when at normal ruiming speed under load. l haveI indicated this iu the diagram Fig. 2. Here the line F' indicates the voltage applied to` the motor and it will be noted that at starting the voltage is considerably below the normal operating voltage at which the motor is intended to operate when at normal ruiming speed under load with the coininutator short circuited. As the speed of the motorI increases the voltage gradually rises until at practicallyggne-half of normal running speed under load it caches the normal operating voltage'. Asl the motor draws nearer to normal ruiming speed under load the voltage is further gradually increased until normal running speed under load is reached and the commutator is sl'ort-circuited when it is considerably above that of normal operating voltage; after which. when the commutator has been short-circuited7 the voltage is gradl ually reduced back to that of normal operating voltage. The current under such circumstaiices is indicated by the curve D. As Will be seen, it starts very inuch below the former current indicated by the line A and after rising slightly at the initial rotations of the motor remains practically constant until normal running speed under load is attained, when it is gradually reduced with the reduction of the voltage. The same may be said of the tbrque when my method is employed. At starting it is` considerably lower than that indicated by the curve B, as the torque of the motor when former methods were employed. lt remains practically const-ant until normal running speed under load is fully reached. Thus, as will be seen oy comparing the curves B and E, giving a high torqueabove the normal immediately preceding the time the motor reaches nor mal running speed under load, after which time, upon the shortcireuiting of the 'commutator, it is gradually reduced with the reduction of the voltage and current hack to the normal. Having explained this portion of my invention, l will now describe the operation of the apparatus oi Fig. 1 in carrying. it out:

Let it be assumed that the pressure across the line wires 20 and 2i and at which the motor is designed to operate at full speed under load, is approximately 208 volts and that when the switch arm 28 rest-s on the left hand.

contact 2'7 the voltages supplied to the motor is 110. At this voltage the motor is started and by gradually rotating the arm 28 over the contacts 27 the normal voltage of 208 is reached. A further rotation of the arm 28 increases this voltage above the normal, so that when the arm 28 rests on the right hand contact 37, the voltage is at its maximum, corresponding to that point of the line ll iininediately above the point Z in Fig. 2.' At this point the short-circuiting ring is clamped upon the commutator as the motor armature has reached full normal running speed under load. A further movement of the arm 28 places it upon the upper one of the contacts 33, completing the circuit through one scction of the auxiliary coil 31 and opposing itl to the coil 24, thus reducing the voltage applied -to the motor. ,d further rotation of the arm 28 finally brings it to the contact 37 and gradually reduces the voltage back to the normal operating voltage of 208 across the mains 20 and 2l by completely cutting the autotransformer coils 24C and 3l from the circuit.

Having fully described my invention, What l claim as new' and desire to secure by Letters Patent of the United States is:

1. The method of operating an alternating current motor7 which consists in starting said motor on a voltage below normal operating voltage, and raising said voltage before normal running speed under load is attained.

2.v rlhe method of operating an alternating current motor, which consists in starting said motor on a voltage below normal operating voltage, and raising said voltage above nerinal operating voltage before normalmunning speed under load is attained.

3. The method of operating an alternating current motor which consists in starting said motor on a voltage below normal operating' IOC senese speed under load is attained and reducing said voltage after normal running speed under load is attained.

5. The method of operating an alternatingr current motor, which consists in starting said motor on a Voltage below normal operating Voltage, raising said voltage above normal operating Voltage before normal running said Voltage to normal operating voltage after said normal running speed is attained.

6. The method of operating an alternating current motor', which consists in starting said motor on a Voltage below normal operating voltage, raising said voltage before current motor, which consists in starting saidmotoi' on a voltage below normal operating voltage, raising said Voltage above iioi'- i mal operating Voltage before normal ruiming speed under load is attained and short-ein cuiting said ymotor when said normal running speed is attained.

S. The method of operating an alternating current motor, whieh consists in starting said n motor on. a voltage below normal operating Voltage, raising said Voltage before normal` l l l l running Speed under load is attained, Short- 'eircuiting said motor, and then reducing said voltage..

9. .lhe method of operating an alternating eurrent motor, which consists in mining the poles in one of the members or said motor at starting and starting said mopredeterspeed under load is attained, and reducing @normal ruiming speed under tor on a voltage below normal operating voitage, and raising said Voltage before normal running speed is attained.

l0. The method of operating an alternating current motor, which consists in starting said motor on commuted cireuit and a Voltage below normal operating Voltage, and raising said Voltage before normal ruiming speed under load is attained;

11. Themetliod of operating an alternat ing current motor, which consists in predetermining the poles of one of tlie members of said motor at starting, and starting said motor by supplying to the other member of said motor a kcurrent below normal operating voltage, raising the voltage of said current above said normal operating voltage before Y load is attained and reducing said voltage after said normal running speed has been attained.

12. lllie method of operating an alternating current motor, whieh Consists in commuting the current in one ol' the members of said motor at starting and starting said motor by supplying to the other member lhereof a cui'- i'ent of a voltage below normal operating Voltage, graduall)T raising said voltage after said motor has started to a point abovey that i .of normal operating if'oltage, short eireiiiting said 'first named member, and graduallT reducing said voltage to normal operating voltage' after normal running speed under load has been attained.

ln testimony whereof, I have hereunto set my hand and affixed my seal in the presence of the two subscribing witnesses.

lNALDO A. ,ln/YYMAN.

Witnesses:

WV. A. ALEXANDER, BnNNn'r'rn Prim.

fr.. s] 

